Lung cancer represents the highest single cause of cancer deaths in the U.S. The ubiquitous airborne carcinogen, benzo(a)pyrene (B(a)P), in combination with various agents, such as ferric oxide has been used in animals to experimentally induce tumors of bronchogenic origin. Recent evidence describes the necessity for this compound, B(a)P, to be metabolized to produce the carcinogenic response. The metabolism of B(a)P in the lung has not been investigated except for the monitoring of one metabolite using homogenization procedures. Since at least 3 enzyme systems are involved in the metabolism of this compound and some of these systems can be inhibited to produce a different metabolic pattern, a study of all the metabolites in the lung is necessary in order to determine if the rate of formation or pattern has changed. An isolated perfused rabbit lung preparation suitable for metabolic studies has been developed in our laboratory and will be utilized.